Identification of a gene involved in the expression of the pathogenic-ity-related gene <I>XC3814</I> in <I>Xanthomonas campestris</I>

Abstract

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of the black rot disease of cruciferous plants. Our previous work had demonstrated that XC3814 is required for full virulence and extracellular polysaccharide production. In this work, the reporter plasmid pL3814sac was constructed by fusing the promoter region of XC3814 to the coding region of the gene sacB, and introduced into Xcc wild-type strain 8004. The resulted strain 8004/pL3814sac was mutagenized randomly by the transposon EZ::Tn5, and 3 mutant strains insensitive to sucrose were isolated. One of the mutants was due to the disruption of the open reading frame XC3882, which was assigned to code a hypothetical protein. To verify whether XC3882 has an impact on the expression level of XC3814, the reporter plasmid pGUS3814 was constructed by fusing the promoter region of XC3814 to the coding region of the gusA gene. This construct was introduced into the wild-type strain 8004 and the XC3882 mutant strain 190A10, which was derived from the transposon Tn5gusA5 insertion. The GUS activity, produced by pGUS3814 in the XC3882 mutant background, was reduced by 81.3% compared to that in the wild type background. These results indicate that the expression of XC3814 is influenced by XC3882.